Fundamental properties of boron carbide
B4C belongs to the trigonal crystal system. There are 12 B atoms and 3 C atoms in the unit cell. The connecting solid diagonals formed by the C atoms in the unit cell are arranged. C is in an active state and can be replaced by B atoms to form a replacement solid solution. , and may break away from the crystal lattice to form high-boron compounds with defects.
B4C has a molecular weight of 52.25, contains C21.74%, and contains B78.26%. It is generally gray to black, with a density of 2.519g/cm3, a Mohs hardness of 9.36, and a microhardness of about 50GPa, second only to diamond and cubic boron nitride. Therefore, B4C powder has a very high grinding ability, and its grinding efficiency can reach 60%-70% of that of diamond, which is 50% higher than that of SiC, and is 1-2 times that of corundum.
The melting point of B4C is 2450°C (differentiation). The coefficient of expansion at 1000°C is 4.5×10-6°C-1. The thermal conductivity is 121.4W/m·k at 100°C and 62.79W/m·k at 700°C. B4C is mainly used as abrasives, and hot-pressed B4C products can be used as wear-resistant and heat-resistant parts. In the refractory industry, B4C is mainly used as an additive, such as adding to carbon-bonded refractory materials to act as an antioxidant. Improving the strength and erosion resistance of the green body in unshaped materials.